Integrated flight instrument system



Dec. 3, 1963 E. H. scHRoEDER INTEGRATED FLIGHT INSTRUMENT SYSTEM 4 Sheets-Sheet l Filed May 6, 1959 Dec. 3, 1963 E. H. scHRol-:DER

INTEGRATED- FLIGHT INSTRUMENT SYSTEM 4 Sheets-Sheet 2 Filed May 6, 1959 www YS si QNN NNN N N mmt o u m @NNI Hmlll Dec. 3, 1963 E. H. SCHROEDER INTEGRATED FLTGET INSTRUMENT sYsT Emea may e, 1959 Dec. 3, 1963 E. H. s cHRoEDER 3,112,644

INTEGRATED FLIGHT INSTRUMENT SYSTEM Filed May e, 1959 4 sheets-sheet 4 United States Patent O 3,1li2964i4 ENTEGRA'I'ED Fil Hi" NS'ITRUMENT SYSTEM Everett H. Schroeder, West Redding, Conn., assigner to Kollsman instrument Corporatinn, Elmhurst, NH., a corporation of New York Filed May 6, 195?, Ser. l o. Slild 9 lairns. (Si. 7S-178) This invention relates to the inter-relation of a plurality of aircraft flight instruments and error correctors for these instruments in a novel manner whereby maximum performance of the instruments is realized.

This system is particularly applicable to a system using a duplicate set of instruments and error correcting means therefor for the pilot and copilot respectively of the aircraft. More specifically, the following instruments and correcting means are provided:

(l) A combined airspeed-angle of attack indicator.

(2) An altimeter.

(3) A Mach meter.

(4) A true outside air temperature indicator.

(5 A true airspeed indicator.

(6) A ram air temperature indicator.

(7) A scale error corrector speciically ttor the altimeter.

(8) A computer unit vfor correcting the various instruments for static system errors such as those due to varying angle or attack and Mach number.

(9) An angle of attack sensor.

The essence or' the instant invention is to interrelate the various components set forth above which are provided in duplicate, one for the pilot and one tor the copilot, in a novel mmer.

The following is a list of speciiic novel interrelations between these various instruments:

(Il) The corrected readings of the pilots and copilots altimeters are compared to one another as a check on the accuracy of the other. Responsive to a predetermined difference in the output of these units, a warning signal is initiated and the .cause of the mismatch can be determined. When the faulty unit is found and cannot be corrected, it can be out out of the system and the computer function can be taken over by the single computer which is lett. If necessary, however, both of the error correcting means, including the computer and the scale error correctors, can be completely disconnected Ifrom the system and the altitude, indicated air speed, and Mach instruments can be driven by pure pneumatic means.

(2) Since for most accurate operation, each of the above instruments should be corrected ttor Mach number, the Mach meter is provided with a synchro measuring means, hereinafter `described as a Synchrotel, which has an output corresponding to the Mach number indication. This Mach number signal is delivered to each computer unit which, in turn, delivers a Mach number correction to each of the various instruments requiring such correction.

(3) Both a primary and alternate static pressure conduit means for impressing the static pressure upon the various diaphragm actuating means of the instrument are provided. These two static pressure means are independent of one another and are switched into the system by a switch controlled by the pilot for his static system selection and by the copilot for his static system selection. The respective valve for controlling the static system to be used for the pilot and copilot instruments is further associated with an electrical switch which communicates with the computer unit -or utilizing the computer components correlated with the primary static system or the alternate static system. Thus, it is assured that when on the primary static system, the computer unit will be mali- "ice ing corrections related to 'that primary system, while when on the alternate static system the computer unit will be making the corrections required oi' the alternate static system. it is to be noted that by providing both a primary and alternate static system for each of the pilots instrumen-ts and the `copilots instruments that there is a fourway check between the two computer units available to determine which portion of which computer is delivering an erroneous signal when such an erroneous signal is detected by the warning means described above in item 1.

(4) Since each of the true outside temperature indicator, true airspeed indicator and ram air temperature indicator are actuated responsive to some function of Mach number and temperature, they are each actuated electrically from the computer unit which receives the input signal related to Mach number and delivers the required `function of Mach number required by each respective instrument to that instrument. An externally mounted temperature bulb measures the outside temperature and delivers this to each of the meters in the required manner. The input Mach number function required of each of the meters may be taken from either the pilots computer or the copilots computer when on either the primary static or alternate static system.

Thus, the above noted indicator devices may be energized from a single temperature bulb and a selection of four different sources for their Mach number correction. Therefore, the pilot and copilot may choose the Mach number correction proven accurate by a comparison of the four different systems and energize the pilots indicators as is required.

(5) A single measurement by an angle of attack sensor is utilized to `drive an angle of attack indicator mounted in a novel manner on an airspeed-angle of attack indicator.

This same signal is applied to each of the pilot and copilot computer units responsible for the static system correction of the altimeter.

(6) The true outside air temperature is measured by a true outside air temperature indicator which has inputs from the Mach meter and an externally positioned ternperature bulb. Since the true airspeed indicator and the ram air temperature indicator both operate in accordance with some function of the temperature, these functions are taken from the true outside air temperature indicator, thus, doing away with the requirement for temperature measuring bulbs for each of the true airspeed indicator and the ram air temperature meter.

Accordingly, the primary object of this invention is to provide a novel integrated -ight instrument system.

Another object of this invention is to combine the varous outputs of instruments `and error correcting means utilized in a ilight instrument system, so that the outputs of certain of the instruments may be utilized in the operation of other instruments.

Another object of this invention is to provide duplicate instrument and error correcting means for the pilot and copilot wherein the operation of the various instruments may be compared and warning means actuated responsive to a predetermined deviation in the pilot instrument readings and the copilot instrument readings.

A further object of this invention is to pnovide a novel ilight instrument system wherein a computer unit operating the pilots instruments and a computer unit operating the copilots instruments may have their outputs compared so as to detect the malfunctiom'ng of one of the units.

Another object of this invention is to provide a primary `and alternate static pressure system for driving various instruments within a ight instrument system having a computer means .for making computer corrections of the instrument reading wherein the computer means has a iirst and second computer device corresponding to the primary and alternate static systems which are automatically switched in response to the switching of their corresponding pressure system.

Another object of this invention is to provide a Mach number signal from a iirst andV second Mach meter and applied to a iirst and second respective computer, which computers selectively deliver an output signal to instruments requiring this correction.

A still further object of this invention is to provide a novel integrated flight system having an angle of attack sensor means which delivers a signal to drive an angle of attack indicator mounted on the same instrument as the airspeed instrument indicator in a novel manner, and to further utilize the angle of attack signal to drive the computer which, in turn, corrects the reading of an altimeter.

A still vfurther :object of this invention is to provide a novel integrated flight instrument system wherein a true outside air temperature meter measures and corrects tem` peratures and supplies required functions of that temperature to either or both of a true lairspeed indicator and ram airspeed indicator and any similar indicating devices requiring some function of temperature for the driving thereof.

Another important object of my invention is to provide a novel integrated flight system wherein basic uncorrected information is furnished through conventional mechanical and pneumatic means and the reliability of the instrument is unaffected by electronic refinements required for extreme accuracy and additional information.

Still another object of my invention is to provide a novel flight system wherein duplication of instrumentation which is usually encountered in obtaining the same data individually is avoided by combining all necessary components into a single integrated system.

These and other objects of my invention will become apparent from the following description when taken in connection with the drawings, in which:

FIGURES 1 and 1a schematically show a preferred embodiment of the integrated ight system of the invention.

FIGURE 2 shows the View of the dial and indicating pointers of the novel combined airspeed-angle of attack indicator of FIGURE 1.

FIGURE 3 shows a perspective v-iew of the Mach meter of this invention.

lFIGURE 4 shows a typical cam for the error correcting computer of the system.

FIGURES 1 and la set forth a schematic diagram of a preferred embodiment of this novel integrated flight instrument system. Before discussing the novel correlation between the various instruments shown in FIGURE 1, a discussion of Ieach individual instrument will be given first.

In general it will be noted that the pilots instruments are set forth on the left-hand side of the figure, While the copilots instruments, 'which duplicate the pilots instruments, are set forth on the right-hand side of the diagram. In the following description the pilots instruments and the copilots instruments will be identified with distinctive numerals, while the internal mechanism of these instruments will be identied with similar numerals, since a description of any particular instrument is true of either the pilots or the copilots instruments.

Az'I'Speed-Angle of Attack Indicator Both the pilot and copilot have identical air speedangle of attack indicators and 22 respectively, as shown in FEGURE l, with the instrument face shown in FIGURE 2. This instrument presents the pilot and the copilot and on a single display, the indicated airspeed, the maximum permissible speed and the angle of attack. Thus, the instrument display seen generally at numeral 24 is comprised of a maximum speed pointer 26, an

i indicated airspeed pointer 2S and an angle of attack indicator 30.

The maximum allowable speed indicator is operable from an altitude diaphragm 31, as schematically indicated, which is externally subjected to the outside static pressure which is introduced into the housing 20 through a conduit 32.

Since the maximum speed pointer responds only to static pressure and it is an indicated airspeed presentation by Way of such number limitation or equivalent airspeed limitation, whichever is the limiting factor at the particular altitude, the desired motion of this pointer with respect to pressure altitude may be controlled along a predetermined pattern by appropriate connecting linkage between the pointer 26 and the diaphragm 31. For eX- ample, between 5,000 and 30,000 feet the aircraft speed may be limited by equivalent airspeed, while from sea level to 5,000 feet by a limiting indicated airspeed, and when above 30,000 feet the limitation might be that of the Mach number.

Hence, on a single respective instrument, both the pilot and the copilot have a comparison between the indicated airspeed of pointer 28 and the maximum allowable speed of pointer 26, and they may operate the aircraft accordingly. It is further important that the pilot know the angle of attack of the aircraft and whether he is above or below approach yand stall angles, as indicated by the movable segment 30.

The angle of attack segment 30 may have positioned thereon a first and second indication indicated by lines 3S and 40 respectively which correspond to an approach speed and stall speed respectively, these lines being positioned with respect to the calibrated airspeed around the airspeed dial. This may be more clearly understood from FIGURE 2 which shows the display Z4 wherein the airspeed is logarithmically calibrated around the circumference of the display dial.

In the particular illustration set yforth in FIGURE 2, the approach indication 3'8 has been set to correspond to an angle of attack of 9 degrees while the sta-ll indication d@ is set to correspond at an angle of attack 22 degrees. In reading the above dial, the maximum permissible airspeed as given by .the maximum speed pointer 26 is 330 knots, the indicated airspeed is 265 knots as given by indieating airspeed pointer 28, while the angle of attack indieating segment 3d shows that the approach speed is slightly lower than the existing speed. Note that actual speed values cannot be :read yon the angle of attack markers and these markers only show whether the pilot should increase or decrease airspeed to getto the angle of attack designated by the marker.

The angle of attack indicating segment 30 is, as seen in FIGURE 1, ,driven from an angle of attack sensor 42. That is to sa* the angle of attack sensor 42 delivers a signal to the stator of a synchro device 44. A difference between `the angular displacement between the rotor and stator of device die creates an error `signal which is amplified by amplifier 45 to thereby drive motor 48 which is in turn mechanically connected to position the angle of attack segment However, motor 4S is further connested to position the stator of Synchrotel dit as it positions angle of attack indicator segment 30 lto bring the error signal back to zero. As soon as the angle of attack segment 3% is properly positioned, the error signal due to a mismatch between the rotor and stator of servo 44 which was initially cai ed by angle of attack sensor 42 is brought to zero and the angle of attack indication is in accordance with the signal delivered by angle of attack sensor 21. Details of the manner in which the angle of attack sensor operates are well known to the art and need not be further described.

It is to be further noted that the angle of attack sensor also is used for correction of certain static system errors. For this purpose a separate synchro in the sensor sends angle of attack measurements -to the computer'.

Altimeter As further shown in FIGURE 1, both the pilot and copilot have an altimeter 50 and 52 respectively. The specific altimeter set forth in FIGURE 1 has been fully disclosed in copending application Serial No. 612,780 filed September 28, 1956 entitled Aircraft lInstrument-Remote Control-Fail Safe in the name of James W. Angus and will be only briefly described here.

rI'hus, the altimete-r comprises a display 54 having an altitude indicating pointer 56 and a drum showing thousands of feet which are driven from a diaphragm 5S which is externally exposed to static pressure over the conduit 76. The diaphragm operated mechanism is rotatably mounted with respect to the indicating dial, as has been set forth in the above noted copending application. The mechanism is rotated and thus the pointer 55 rotates therewith by electrically c erated `servo-correction means responsive to scale error corrections for the particular angle of attack and Mach number of the aircraft.

These inter-relations, however, will be set forth more fully hereinafter, it being sufiicient to understand at this point that the electrically driven servo-mechanism is associated with a spring return mechanism 69 which will return the altimeter to uncorrected pneumatic Ioperation under control of diaphragm 5S when electrical power is removed,

Mach Number Indicator Both the pilots arid copilots instruments are provided with a Mach number indicator and transmitter 7% and 72 respectively which is comprised of an external housing having a first diaphragm 75l therein which is externally exposed to static pressure from the conduit 76, and a second diaphragm 73 which is externally exposed tothe static s'fstem pressure from conduit 7c and is internally exposed to pressure of Pita-t 3e over the conduit Et.

The outputs of the two diaphragms 74 and '73 are ccmbined to position Mach number indicating pointer el of display Sd in the manner set forth in Fi-SURE 3 and schematically indicated in FIGURE 1.

To fully understand the Mach meter operating mechanism of FEGURE 3 it is to be first understood that the Mach number M is given from the following equation:

M is ythe flight Mach number, Ap is the pressure diierential between the stagnation pressure at the head of the Pitct tube and the static pressure corresponding to the aircrafts altitude, and p1 is the static pressure conresponding to the aircraft altitude.

Accordingly, in the Mach indicator of FlGUPlS 1 and 3 the dierential pressure is measured Ain diaphragm 78 which, as best seen in FGURE l, is positioned in accordance with the difference in Pitot tube pressure and static pressure, while the static pressure is measured by diaphragm 74- which is evacuated and has the static pressure applied externally thereto over the static conduit 76.

Referring now to 'FIGURE 3, it is seen that dierential pressure diaphragm '78 is connected to move a slidably mounted adjusting bracket assembly 'S6 which has an extending arm 88 mounted thereon. Arm is engageable with respect to a perpendicular arm 9% which in turn is fastened to a sliding rocking shaft assembly 92 which is slidably mounted in fixed supports 94 and 96. Sliding rocking shaft assembly 92 is further biased to rotate in a counterclockwise direction by a biasing spring assembly 9S, this motion being prevented normally by the engagement between arms SS and 9G.

Rocking shaft assembly 92 then has a further arm flti erpe-ndicularly fastened thereto which is `engageable with arm 192 which is fastened to a pivotally mounted shaft iti-i which has a counter-balanced gear sector 166 mounted thereon and is biased to rotate in a counterclockwise direction by biasing spring assembly lS, this rotation being normally prevented by the engagement between mms 169 and 162. Gear sector `1% then engages a hand- StaE pinion 11i? which has a pointer 112 mounted thereon.

The rotor of Synchrotel device 114 of FIGURE 1 is mounted between pinion and pointer 112 so as to rotate responsive to rotation [of the shaft 112, but is omitted from FifiT J5 3 for the sake of clarity. However, it is to be understood that the Synchrotel device will have an output proportional to the Mach number indicated by pointer 112.

The positioning of pointer 112 through the above noted linkage as actuated by the differential pressure diaphragm 7% is corrected for static pressure by means of diaphragm 74 which turns an altitude rocking shaft assembly 116 responsive to expansion or contraction of diaphragm 74.

Altitude rocking shaft assembly 116 has an output arm 113 fastened thereto which engages one end of sliding rocking shaft assembly 92 whereby sliding rocking shaft assembly 92 is axially positioned responsive to rotation of arm 11S. This axial position of `assembly 92 will move the point at which arm 1d@ engages arm 102, thus varying the effective lever arm of arm 162 so as :to control the rotation imparted to sector 1%5 responsive to a rotation of `arm lili?.

It has been found that with this type of linkage and with `the arm dimensions properly proportioned, the above noted Mach equation is satisfied over lan appreciable range of ratio of differential pressure to static pressure. Thus, in operation, if the indicated -airspeed of the aircraft increases, the differential pressure diaphragm 78 expands to thus allow a counterclockwise rotation of assembly 92 `and a clockwise rotation of shaft 104 and sector 1%. This in turn drives pointer 112 in a counterclockwise direction which, when seen from the other side of the pointer, corresponds to an increase in Mach number.

To compensate for changes in altitude, if the static pressure diaphragm expands due to an increase in altitude, the assembly g2 will be driven forward and the effective lever arm of Iarm 182 will be decreased. Therefore, for a particular change in indicated airspeed, the change in Mach number will be decreased.

in summary, therefore, the Mach meter of this novel integrated flight system positions a pointer through static measuring means. Since, as will be seen hereinafter, the Mach number yof the aircraft is important in other instrument corrections and instrument readings, the Mach number pointer has a synchro device attached thereto whereby an electrical signal is generated yand is to be subsequently utilized in these various electrical corrections.

Accordingly, each of the corrected instruments need not have their own pneumatic measuring system for Mach number and substantial duplication of equipment is avoided.

Computer Units and Primary and Alternate Static Pressure Conduit Means The three previously described instruments for both pilot `and copilot (the airspeed-angle of attack indicator, the altimeter land the Mach indicator and transmitter) are the only three instruments within this novel integrated flight instrument system which require pressure inputs. The other instruments, as will be seen hereinafter, utilize functions previously computed within these above three instruments plus a temperature bulb for their own operation and are independent of other pressure systems.

The computer units for conventing angle of attack measurements from iangle of attack sensor 42 and Mach number from `the Mach number indicator and transmitter 7f3 and 72 and for providing static error correction for the altimeter into useful electrical signals are the identical computer units 120 and 122 for pilot and copilot respectively.

Each of these computer units includes two three-dimensional cams 124 and 126 wherein the iirst corresponds to a primary static system and the second corresponds to an alternate static system.

IMore specically, cams 124 and 126 position a cam follower which in turn mechanically positions a synchro in accordance with the measured angle of attack and measured Mach number, as will be more fully described hereinafter. The cam surface is independent upon the predetermined static characteristics of its respective static system, and fthe data for it is determined empirically or calculated for each airplane type.

A typical cam structure is shown in lFIGURE 4 in perspective for a disk type cam which is a disk 31% having a central mounting aperture EQ2 which receives a pivotal mounting means. A cam follower 304 rides on the cam surface 306 of disk 3th), its vertical position being an indicia fof the required correction signal. T he cam surface 366 is contoured in accordance wi-th predetermined flight characteristics of the aircraft, as described in copending application Serial No. 612,780 tiled September 28, 1956, with a typical contour being shown by'contour lines 36S in lFIGURE 4. The ventical position of follower 3134 will, therefore, depend upon the angular position of disk th about its pivot 3122, and the radial distance of follower l3&4 from pivot 302. As is schematically illustrated in 'FIGURE 1, the angular position of disk 390 will be determined as some function of Mach number, while the radial position of follower 31.54 may be determined by some function of airspeed.

In accordance with the invention, both a primary static system having conduits 12d and 139 as inputs therefor for the pilots instruments and copilots instruments respectively and an alternate static system having conduits 132 and 134 respectively for the pilots instruments and the copilots instruments respectively are provided. lt is important that the proper three-dimensional cam 124 and 126 is utilized in conjunction with its previously callbrated primary static system or alternate static system. In order 4to assure that fthe proper cam and static system for each of the pilot and copilot instruments is ntized, a novel static system selector 136 and 133 respectively is used for fthe pilot and copilot respectively.

Each of static system selectors 136 and 13S comprise a valve mechanism wherein the primary static system or alternate static system may be alternately connected to an output static sys-tem conduit 14% or 142 respectively, these output conduits being applied to the various instrument casings. The same valve or operating handle that operates the conduit valve, however, is ganged to operate electrical switches 144i and 145 respectively, for pilot and copilot lrespectively, wherein switch 144 is movable'from -a normal position to an alternate position corresponding to the output of cam 124 or 126 respectively.

Accordingly, when the primary static system is selected within either of static system selectors 136 and 133, the primar-y static system cam 124 is necessarily used as the computer unit output device.

ISimilarly, if the alternate static system is selected within the static system selector unit, the alternate cam 126 is necessarily util-ized in the computer unit.

Both the pilot and copilot are provided with scale error correction systems 14S fand 159 specifically for their altimeters 50 and 52 respectively. These scale error correctors comprise an adjustable cam surface 152 which is calibrated in conjunction with the particular altimeter associated therewith. An adjustable cam surface 1152 is positioned by servo motor 154 which is operated by a signal Y from Synchrotel i156 which is attached to the altimeter pointer within casing Si? or 52 respectively, and a synchro which is driven by the adjustable cam tends to decrease the error signal to Zero. This error sivnal is, of course, amplified in the usual manner by amplifier 153 whereby motor 154 drives adjustable cam 152 until the cam is positioned in accordance with the position of altimeter pointer 56.

The position of adjustable cam l152 is transmitted to a cam follower 16d' which in turn adjusts a differential synchro which adds a static error signal from the computer unit to the scale error correction signal, as described in the above noted copendinfay application, and the differential synchro then operates to position a servo `162 Within altimeters Sii (-52) to subsequently cause a motor 164- to rotate the mechanism body of the altimeter, as seen in copending application Serial No. 614,670, `tiled October 8, 6 so that pointer 56 will move with respect to its indieating dial so as to electrically correct the altimeter for scale error correction.

The three-dimensional cams are so operated that they are rotated in accordance with the Mach number indication and are axially translated responsive to the angle of attack indication. More specifically, the output of Synchrotel-1'14 which is an :electrical indication of Mach number is applied for example to the stator of synchro 16d. Because of the displacement between the rotor and the stator of synchro 16h an electrical signal is applied to ampiier y162 and thereafter to servo motor 164,

Servo moto-r 164 then rotates to rotate both the rotor of synchro l1653' and three-dimensional cams 124 and 126 until such a time that the rotor and stator deliver no further electrical out-put signal and the cams are angularly positioned in accordance with this predetermined Mach number.

1n a similar manner, the signal from the angle of attack sensor 42 is applied to a synchro 166 which drives motor through amplier 17? until the cam surfaces driven by the motor in a transverse direction are properly positioned.

Thus, both angle of attack and Mach number serve to position the three-dimensional cam surface of cams 124 and 126 in a predetermined position whereby the cam followers '172 and 174 are appropriately positioned.

Cam followers 172 and 174 are shown as being connected to synchros 176 and 17S respectively which impress a signal on their respective diterential synchros in their respective scale error correctors to subsequently aid in the position-ing of the altirneter mechanism bodies through motor 164.

It is to be noted that synchro :176 related to cam 124 of the pilots primary static system is operable only when switch 144 is in the normal position and the primary static system is in use. Similarly, cam 126 is operable only when switch 146 of the copilots static system selector is in the alternate position.

vIn a similar manner, the computer unit l122 of the copilots instruments has cam 126 operable only when the pilots static system selector is in the alternate position, and the cam 124 which is operable only when the copilot static system selector is in the normal or primary static system position.

T me Outside Air Temperature Indicator Both pilot and copilot have true outside air temperature indicators 186 and I1% respectively available to them as shown in FIGURE lA. The copilots true outside air temperature indicator hereinafter denoted as the TOAT indicator is driven from the output `of the pilots indicator 186 by a synchro means, as will be described hereinafter.

TOAT indicator 1186 is the indicator which receives all the information required to measure the true outside air temperature. The true outside air temperature indicated by indicator pointer 1% is computed from the relation T (Indicated) l -l- 0.2111111 2 The :indicated temperature or T (Indicated) is measured by the temperature bulb 192 which is mounted eX- ernally of the aircraft in some predetermined position.

The Mach number M required in determining the true outside air temperature is derived from either computer l2) or .22 which, as will be described hereinafter, calculates the denominator of the above noted equation and supplies it to the instrument.

The temperature to which temperature bulb 19.2 is eX- posed adjusts the resistance of resistor nd contained therein so as to vary the total resistance of parallel connected resistor i194 and resistor dt which is in `one leg of the Wheatstone bridge circuit shown. The adjacent leg of the Wheatstone bridge circuit receives the func-tion l-i-OZKMZ.

When the bridge is unbalanced, an output voltage is delivel-ed from die input voltage source or the bridge to arnplilier 260 which drives a servo system including servo motor 2d?. and synchro 294. The motor 2d?. is connected to vary the movable arm .2% of potentiometer 2% in such a direction as to balance the bridge circuit and bring the output voltage of the bridge to zero. -lt will be understood by those skilled in the art that the adjustment of the potentiometer under voltage balanced conditions will be proportional to T (indicated) divided by (1+0.2K1M2).

The motor 262 positions the TOAT indicator pointer lji, as schematically indicated, as well as synchro 264 which is used to transmit the indication to the slave indicator. 'Once this zero condition is reached, it is clear that the TOAT indicator pointer i9@ is positioned at the appropriate value equal to the true outside air temperature.

rl'he synchro Itransmitter Zli is connected to the copilots slave TOAT indicator i3d through the connection including follower synchro 2li) which positions pointer 2.7;2 of indicator in accordance with the positioning of servo :which is functionally related to the position of pointer 19t).

it is to be further noted that motor 2h52, in positioning pointer i951?, further adjusts potentiometers 2li/i and 2id to supply electrical parameters which are proportional to the true outside air temperature and the square root of the true outside air temperature respectively. rhese two functions, as will be seen hereinafter, are utilized in the rain air temperature indicator (RAT) and the true airspeed indicator (TAS) respectively.

True Airspeed Indicator ri'he pilot and copilot each have a true airspeed indicator 2idand 21o respectively Where the copilots indicator 2id is a slave indicator driven by the pilots indicator 2id. Since true airspeed is computed from the equation a Wheatstone bridge computer device having the square root of the true outside air temperature and the Mach number as inputs is provided.

The liti-ach number is, :as lwas the case in the TOAT indicator, taken from either of computers l2@ or L22, and the signal proportional to the square root of the temperature is tali-en from potentiometer 21e oi the TOAT indicator. in this case, the two signals are applied to oppocl g legs of the bridge, and the bridge may be balanced by adjusting movable arm l5 of potentiometer 22% to Igive an indication or" the product of the two inputs. The potentiometer 222 is utilized as a ranging adjustment for the instrument.

The output of the bridge is applied to the servo system including amplier 22d, servo motor 225 and synchro 228 which are inter-elated in the well known manner to drive a digital type of indicator 23?. rhus, as a signal appears on the output or the bridge indicating a change in either Mach number or true outside air temperature, the motor E26 is energized so as to operate synchro 228 to bring the bridge :back to balance by varying potentiometer 22d and, at the same time, oA crates the digital indicator 23@ to display the true airspeed.

As was the case with the TGAT indicator, transmitter l@ synchro 223 is associated with a repeater synchro 232 of the slave true ai-rspeed indicator 216 to thereby position indicator 234 in accordance with the reading or" indicator 239i.

Ram Air Temperature t/eosuremerzt The pilot and copilot further have ram air temperature indicators 236 and 23% respectively, where indicator 23S is a slave indicator driven by the pilots indicator 236. Ram -air temperature may be computed from rR,m=r (prezioso) Similar to the `case in indicator 214, a Wheatstone bridge is utilized in multiplying the square root of the true outside air temperature taken from potentiometer Zlti and the quantity l-i-OllzMZ taken from either computer 12%? or 22.

The ram air temperature indicator bridge circuit further includes a ran-ge adjusting potentiometer 246 and a servo driven potentiometer 2d?. utilized to balance the bridge when there is an output signal. The servo system includes the amplier 24d, servo motor 246 and synchro 243 Where fthe motor 246 drives each of the potentiometer 242, servo Zed and indicating [means 25% so as to maintain a zero output signal from the bridge.

As was the oase Wit-h instruments 86 and Ell-l, synchro 243 is associated with a repeater synchro 252 which drives indicator 254 of the copilots slave ram air temperature indicator 238i.

Integration of Instruments From the foregoing, `certain novel -features of this invention have become apparent. it is now possible to des-crine the other novel features heretofore mentioned in the integration of the various components.

The iirst of these novel features is the manner in which the pilots computer E2@ `and the copilots computer 122 may be checked against one another so as to indicate the maliunctioning of one of tie computers. This novel correlation is achieved by taking the outputs from synchros in the two sca-le error correctors which actually repeat the positions of the two altimeter pointers which have been corrected yby the computer. if the system were perfect, these synchros, as well as the altimeter pointers, would have the lsame position. ln the event of a mismatch which would indicate the maliunctioning of one of the systems, a warning ligit 25?. will be energized through an appropriate energizing means 25% which could be a switching device.

The second novel manner in which the various ins rurnents are correlated is in the derivation of a Mach number signal from the Mach number measuring means 7G. As has been previously described, a Mach number signal is required for the operation oi the three-dimensional cams 124i and'iZd of computers l2@ and i2?. respectively, and it is further needed in the operation of the true outside air temperature indicator, the true airspeed indicator and the ram air temperature indicator.

In accordance with the instant invention, the Mach number is pneurnatically measured a single time by instrument 7i), and Synchrotel lid is positioned in accordance rwith this measurement. The output of Synchrotel 114 then operates the yservo system including synchro 160, amplilier to2 and servo motor 16d where servo motor 164i drives the cams i241' and 125. However, it is also seen that motor 364 positions potentiometers 264, 266 yand Zeb respectively, as sho-wn in FIGURE 1.

Potentiometer 264 is calibrated to deliver a signal proportional `to l-j-OZKMZ. Thus, Ias the Mach number M varies, the resistance of potentiometer 264 varies in accordance with the above noted relation. This function is then transmitted through a computer selector switch 279 contained within switch panel 272, `and is selectively dellivered to the true outside air temperature indicator ld. More specically, when switch 2.7i? is turned to 13, the

l l 1%().2Kl/l2 signal is taken from com-puter 3.2i), When however, the switch is urned to C, the l-l-OZKM signal is taken from the copilots computer i225.

Potentiometer 265, as indicated in FlGUlE l, delivers a signal proportional to the Mach number M, and is delivered to the true airspeed indicator which requires this signal through the switch which selects either the pilots computer l2@ or the copilots computer Finally, potentiometer 258 which supplies a signal l-l-OlKr i2 is connected to the rain air temperature indicator through switch 75.

Accordingly, by making a single Mach number measurement in Mach number indicators '70' or 72, the Mach number is transmitted to a plurality of dii'erent instruments requiring different functions of the Mach number.

As has been stated above, both a primary static system and alternate static system are provided for driving the pneumatic-responsive instruments of the system. rThe primary and alternate systems are associated with a respective computer cam P124 or 26, and the valve selecting means E35 for the pilot and i3?, for the copilot is ganged to an electrical selecting switch so that the appropriate computer cam is always utilized with the proper pressure system.

A further novel correlation provided in this novel integrated system has been heretofore described in conjunction With the electrically operated TOAT, TAS and RAT indicators. In general, this novel integration is seen to comprise a single measurement of the true outside air temperature by instrument ltd-5. This measured value is then translated into functions of the true outside air temperature winch are required by the TAS indicator and RAT indicator by means of potentiometers 214. and 216 respectively.

Therefore, each of instruments 11S-3, le and 2,33 are slave-driven instruments corresponding to the TOAT indicator 185, the TAS indicator Zli and the RAT indicator 235 respectively of the pilots instruments.

A further feature of this integrated flight system is that a single angle of attack measurement by the angle of attack measuring sensor 42 is utilized in driving both the angle of attack indicators Ztl and 22, as Well as driving the angle of attack signal required for the static correction of computers 1Z0* and 122. Accordingly, it is once again seen that unnecessary duplication of equipment is avoided.

Although I have described pr t:erred embodiments of my novel invention, many variations and modiiications will now be obvious to those skilled in the art, and I refer therefore to be limited not by the specific disclosure herein but only by the appended claims.

What is claimed is:

l. ln an instrument system; an instrument having a pressure input means, a rst and second source of pressure connectable to said pressure input means, and a first and second automatic instrument correctiong means; said tirst instrument correcting means being calibrated for correcting the reading of said instrument when said instrument pressure input means is connected to said iirst source of pressure; said second instrument correcting means being calibrated for correcting the reading of said instrument when said instrument pressure input means is connected to said second source or pressure; a pressure source selector; said pressure source selector being connected between said pressure input means and said tirs-t and second source of pressure and being operable to selectively connect either said iirst or said second source of pressure to said pressure input means; an instrument correcting means selector; said instrument correcting means selector being operably connected between said instrument and said :first and second instrument correcting means to selectively connect one of said first or said second instrument correcting means to said instrument; said pressure source selector being operatively connected to said instrument correcting means; each of said pressure source scl2 lector and said instrument correcting means selector being simultaneously operable to insure that said iirst instrument correcting means is connected to said instrument when said tirst pressure source is connected to said instrument and that said second instrument correcting means is connected to said instrument when said second pressure source is connected to said instrument.

2. In an instrument system; an instrument having a pressure input means, a rst and second source of pres- Sure conncctable to said pressure input means; and a i'irst and second automatic instrument correcting means; said r'irst instrument correcting means being calibrated for correcting the reading or" said instrument when said instrument pressure input means is connected to said irst source of pressure; said second instrument correcting means being calibrated for correcting the reading or" said instrument when said instrument pressure input means is connected to said second source ot pressure; a pressure source selector; said pressure source selector being connected between said pressure input means and said first and second source of pressure and being operable to selectively connect either said first or said second source of pressure to said pressure input means; an instrument correcting means selector; said instrument correcting means selector being operably connected between said instrument and said 'irst and second instrument correcting means to selectively connect one of said rst or said second instrument correcting means to said instrument; said pressure source selector being operatively connected to said instrument correcting means; each of said pressure source selector and said instrument correcting means selector being simultaneously operable to insure that said iirst instrument correcting means is connected to said instrument when said -rst pressure source is connected to said instrument and that said second instrument correcting means is connected to said instrument when said second pressure source is connected to said instrument; said pressure selecting means including a valve, said instrument correcting means selector including an electrical switch; said valve and electrical switch being ganged for simultaneous operation.

3. yIn an instrument system; an instrument having a pressurVV input .me-ans, a nrst and second source of pressure connectablc to said pressure input means, and a -rst and second automatic instrument correcting means; said iirst instrument correcting means being calibrated for correcting the reading of said instrument when said instrument pressure input means is connecte-d to said iirst source of pressure; said second instrument correcting means being calibrated for correcting the reading of said instrument when said instrument pressure input means is connected to said second source of pressure; a pressur source selector; said pressure source selector being connected bet-Ween said pressure input means and said iirst and second source of pressure and being operable to selectively connect either said iirst or said second source of pressure to said pressure input means; an instrument correcting means selector; said instnument correcting means selector being opcrably connected between said instrument and said lirst and second instrument correcting means to selectively conn ct one or said first or said second instrument correcting means to said instrument; said pressure source selector being operatively connected t0 said instrument correcting means; each of said pressure source selector and said instrument correcting 'means selector being simultanecusly operable to insure that said first instrument correcting means is connected to said instrument Iwhen said rst pressure source is connected to said instrument and that said second instrument correcting means is connected to said instrument when said second pressure source is connected to said instrument; and a manually operable switch for `operating both of said pressure source selector and said instrument correctin means selector.

4. ln an instrument system; a lirst and second instrument having a first and seco-nd respective input means; a iirst and second source of pressure connectiole to each of said first and second respective input means; and a irst and second automatic instrument correcting means for each of said first and second instrument; said rst instrument correcting means being calibrated for correcting the reading of said irst and second instruments when drivenby said first source of pressure; said second instrument correcting means being calibrated tor correcting the reading of said tirst and second instruments when driven by said second source of pressure; a pressure source selector and an instrument correcting means selector; said pressure source selector selectively connecting either of said rst or said second source of pressure to said input means of said first and second instrument; said instrument correcting means selector selectively connecting either of said lirst or said second instrument correcting means to said iirst and second instruments; said instrument correction selector means and said pressure selector means being operatively connected to one another for simultaneous operation.

5. -In an instrument system; a first and second instrument having a first and second respective input means; a first and second source of pressure connectible to each of said irst and second respective input means; and a first and second automatic instrument correcting means for each of said tirst and second instrument; said first instrument correcting means being calibrated for correcting the reading of said first and second instruments when driven by said rst source of pressure; said second instrument correcting means bein-g calibrated for correcting the reading of said rst and second instruments when driven by said second source of pressure; a pressure source selector and an instrument correcting means selector; said pressure source selector selectively connecting either of said first or said second source of pressure to said input means of said first and second instrument; said instrument correcting means selector seiectively connecting either of said rst or said second instrument correcting means to said rst and second instru-ments; said instrument correction selector means and said pressure selector means being operatively connected to one another for simultaneous operation; said pressure selecting means including a valve, said instrument correcting means selector including an electrical switch; said valve and electrical switch being `ganged lfor simultaneous operation.

6. In an instrument system; a first and second instrument having a iirst and second respective input means; a iirst and second source of pressure connectible to each of said first and second respective input means; and a rst and second automa-tic instrument correcting means tor each of said first and second instrument; said t'irst instrument correcting means being calibrated for correcting the reading of said iirst and second instruments when driven by said first source of pressure; said second instrument correcting means being calibrated for correcting the reading of said tirst and second instruments when driven by said second source of pressure; a pressure source selector and an instrument correcting means selector; said pressure source selector selectively connecting either of said rst or said second source of pressure to said input means of said first and second instrument; said instrument correcting means selector selectively connecting either 'of said rst or said second instrument correcting means to said rst and second instruments; said instrument correction selector means and said pressure selector means being operatively connected to one another Afor simultaneous operation; said pressure selecting means including a valve, said instrument correcting means selector including an electrical switch; said valve and electrical switch being ganged for simultaneous operation; and a manually operable switch for operating both of said pressure source selector and said instrument correcting means selector.

7. An aircraft instrument system; said aircraft instrument system including `a rst instrument and second duplicate instrument and a first and second correcting means to correct the reading of said first and second instruments respectively; each of said iirst and second correcting means having a first and second input parameter, each of which determine the required correction of their respective instrument readings; each of said iirst and second correcting means generating a corrective signal in accordance with said input parameters; mechanism operated by said corrective signals connected to said iirst and second instruments respectively for correcti-ng the reading of said instruments; and means `for selectively connecting said first and second correcting means to one of said instruments whereby the operator may compare said corrective signals of said iirst correcting means to the correcting signals of said second correcting means to determine an inaccuracy in either of said irst or second correcting means.

81. An aircraft instruir ent system; said aircraft instrument system including a tirst instrument and second duplicate instrument and a iirst and second -correcting means to correct the reading of said iirst and second instruments respectively; eac 'of said tirst and second correcting means having a irst and second input parameter, each `of which deter-mine the required correction of their respective instrument readings; each of said rst and second correcting means generating a corrective signal in accordance with said input parameters; mechanism operated by said corrective signals connected to said iirst and second instruments respectively ttor correcting the reading o-f said instru-ments; and means for selectively connecting said first and second correcting means to one of said instruments whereby the operator may compare said corrective signals of said irst correcting means to the correcting signals of said second correcting means to determine an inaccuracy in either of said first or second correcting means; :sa-id Emechanism including a servo means; said corrective signals being selected voltages driving said servo means.

9. An aircraft instrument system; said laircraft instrument system including a tlirst instrument and second duplicate instrument and a first and second correcting means to correct the reading of said first and second instruments respectively; each of said irst and second correcting means having a iirst and second input parameter, each of which ydetermine the required correction of their respective instrument readings; each of said rst and second correcting means generating a corrective signal in accordance with said input parameters; mechanism operated by said corrective signals connected to said rst and second instruments respectively for correcting the reading of said instruments; and means for selectively connecting said tirst and second correcting means to one of said instruments whereby the operator may cornpare said corrective signals of said rst correcting means to the correcting signals of said second correcting means to determine an inaccuracy in either of said first or second correcting means; said comparing means being operatively connected to warning means for initiating operation of said Warning means responsive to a predetermined difference in the corrective signal of said iirst correcting `means and the corrective signal of said second connecting means.

References Cited in the file of this patent UNITED STATES PATENTS 2,126,935 Manteuiel Aug. 16, 1938 2,611,560 Harcum et al. Sept. 23, 1952 2,598,681 Garbarini et al. June 3, 1952 

4. IN AN INSTRUMENT SYSTEM; A FIRST AND SECOND INSTRUMENT HAVING A FIRST AND SECOND RESPECTIVE INPUT MEANS; A FIRST AND SECOND SOURCE OF PRESSURE CONNECTIBLE TO EACH OF SAID FIRST AND SECOND RESPECTIVE INPUT MEANS; AND A FIRST AND SECOND AUTOMATIC INSTRUMENT CORRECTING MEANS FOR EACH OF SAID FIRST AND SECOND INSTRUMENT; SAID FIRST INSTRUMENT CORRECTING MEANS BEING CALIBRATED FOR CORRECTING THE READING OF SAID FIRST AND SECOND INSTRUMENTS WHEN DRIVEN BY SAID FIRST SOURCE OF PRESSURE; SAID SECOND INSTRUMENT CORRECTING MEANS BEING CALIBRATED FOR CORRECTING THE READING OF SAID FIRST AND SECOND INSTRUMENTS WHEN DRIVEN BY SAID SECOND SOURCE OF PRESSURE; A PRESSURE SOURCE SELECTOR AND AN INSTRUMENT CORRECTING MEANS SELECTOR; SAID PRESSURE SOURCE SELECTOR SELECTIVELY CONNECTING EITHER OF SAID FIRST OR SAID SECOND SOURCE OF PRESSURE TO SAID INPUT MEANS OF SAID FIRST AND SECOND INSTRUMENT; SAID INSTRUMENT CORRECTING MEANS SELECTOR SELECTIVELY CONNECTING EITHER OF SAID FIRST OR SAID SECOND INSTRUMENT CORRECTING MEANS TO SAID FIRST AND SECOND INSTRUMENTS; SAID INSTRUMENT CORRECTION SELECTOR MEANS AND SAID PRESSURE SELECTOR MEANS BEING OPERATIVELY CONNECTED TO ONE ANOTHER FOR SIMULTANEOUS OPERATION. 